inlet valve spring breakage on 110 engine in 280GE

Doing an oil change and looked in the oil filler opening and noticed a slightly displaced broken spring.  See photo - the break is on the right, the whole thing should be a continuous loop of metal..  Rather worrying as if the rest of the spring were to break there would then be two loose bits of metal right next to timing chain, valves etc with potential for total disaster.  Took rocker cover off to check the other springs which thankfully were OK.  This engine has done 130,000.  Has anyone seen this problem before?.  Dealer says spare springs are readily available in UK (and not expensive) and should be with me within three days so no big deal but it would be interesting to know if this is a common problem at this mileage on a 110.